Different output for get_class and ::class

[franmomu]

Apparently it's the same, but when the result is used in a call, they behave different:

https://psalm.dev/r/23928709e1

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/23928709e1

<?php

declare(strict_types=1);

interface ObjectManager
{
    /**
     * @template T of object
     * @param class-string<T> $className
     * @return T|null
     */
    public function find(string $className): ?object;
}

function test(ObjectManager $dm): void {
    $obj = new \stdClass();

    /** @psalm-trace $class1 */
    $class1 = get_class($obj);
    
    /** @psalm-trace $class2 */
    $class2 = $obj::class;

    /** @psalm-trace $result1 */
    $result1 = $dm->find($class1);
    
    /** @psalm-trace $result2 */
    $result2 = $dm->find($class2);
    
}

Psalm output (using commit 1f72597):

INFO: Trace - 19:5 - $class1: class-string<stdClass>

INFO: Trace - 22:5 - $class2: class-string<stdClass>

INFO: Trace - 25:5 - $result1: null|object

INFO: Trace - 28:5 - $result2: null|stdClass

INFO: UnusedVariable - 25:5 - $result1 is never referenced or the value is not used

INFO: UnusedVariable - 28:5 - $result2 is never referenced or the value is not used

[orklah]

You're right, get_class is internally handled by TDependentGetClass while ::class creates a TLiteralClassString. I don't really remember why those two are different though.

Seems like one is handled on template resolution but not the other